The objectives of the proposed work are to identify and characterize the immunologic and viral mechanisms by which Aleutian disease virus produces a persistent infection and disease in mink. Aleutian disease virus from naturally and persistently infected ferrets will be tested for pathogenicity in mink. The yield of Aleutian disease virus in cell cultures is low and variable. Viral growth will be assessed in cells from other carnivores, and attempts will be made to improve viral growth with helper viruses. Immunologic characterization of the monoclonal IgG proteins found in some mink with Aleutian disease will be performed.